As is known, the safety chain of literally every elevator comprises a series of switches, all of which must be made (closed) so that the entire safety chain is a closed, conductive circuit, otherwise, the elevator is prevented from operating. In the past, elevator safety chains comprised a plurality of discrete switches, each of which have a moveable contact which connects between a pair of circuits when a parameter is in a safe condition, and which disconnects from at least one circuit in the safety chain when the parameter is no longer in a safe condition. Examples of switches in the safety chain are hoistway door lock switches, elevator door switch, emergency stop switch, inspection switch on the top of a cab, upper and lower hoistway limit switches, and the overspeed switch. The various switches are interconnected by wiring, which in turn must conform to local government regulation codes with respect to size and location of wires and conduits. Furthermore, once a building is wired to provide a safety chain, it is difficult to alter the building configuration, or the architectural design of the landings, due to the imbedded wiring. The elevator and hoistway door lock switches must be mounted on the doors themselves, and therefore are connected by flexible wiring either to the cab or to the building, as the case may be.
To overcome the foregoing and other deficiencies in hard-wired, discrete switch safety chains, a wireless safety chain for elevator systems is disclosed in U.S. patent application Ser. No. 09/899,400, filed Jul. 5, 2001. Therein, each parameter related to elevator safety has a sensor related to a wireless communication means, such as transceivers, so that when the monitored parameter becomes unsafe, the condition of the sensor causes the transceiver to be switched off. A master transceiver related to the elevator controller sends a token to a first transceiver, which in turn will send it to the next transceiver, and so forth. It will not be sent through all of the wireless communication means of the safety chain and back to the master transceiver whenever any parameter is in an unsafe condition; thus, the controller will be informed that an unsafe condition exists. Power for the transceivers may be supplied by hardwire to the building power, by passive battery, or by a battery system which is recharged by inductive coupling, such as with a recharging circuit disposed on the elevator car. Use of hardwired power obviates the advantage of a wireless system, in that wires supplied for power are as inconvenient as wires interconnecting the safety chain switches. Battery operation requires far too much maintenance, cost and environmental impact. Inductively coupled recharging systems are complex and unreliable.
The foregoing analysis is applicable as well to call buttons, in the car and at the landings.